This is a mod for those who already are bored with the constantly sun shining weather.
It's a simple mod that everyone can do but it takes a s..t load of time to balance everything together.
I strongly recommend using HDR for it, cause that's where the magic happens.
Bare in mind that it's a mod and because of that it's far away from being perfect so you want to keep the day time between 10 and 16 hours and the track temperature close to 10 C.
To run this mod - create two additional folders in your AC installation folder / system / cfg
and name them "about to rain" and "sunny".
Move you original "colorCurves" and "weather1" to the sunny folder and the modded files that you just downloaded to the "about to rain folder".
This way you will be able to switch between the sunny and rainy weather in no time.
To switch weather simply go to the corespondent folder, copy all files and paste the to your AC installation / system / cfg folder.